Formation of interfacial structure of Sn-3.7Ag-0.9Zn eutectic solder with different Al additions

摘要

The structural evolution of interfaces between the Sn-3.5Ag-0.9Zn-xAl (x = 0.5 and 1.0) solders and Cu substrate has been investigated by microstructural observations. The results suggest that the addition of Al in the Sn-3.5Ag-0.9Zn restrains the formation of Cu_5Zn_8 inter-metallic compounds (IMCs) at the soldered interface. Moreover, the formation of Al_2Cu and Cu_9Al_4 IMCs leads to a crack failure near the interface of the Sn-3.7Ag-0.9Zn-1Al and Cu pad. It is suggested that the increase of Al content (e.g. 1 wt%) in the Sn-Ag-Zn eutectic solder would do harm to the reliability of the solder joint.